For aesthetic, safety and legal reasons, the contents placed on an open and exposed bed of a truck should be covered. In fact, there are numerous ordinances and laws in jurisdictions throughout the United States which require the covering of loads.
The most common of these covers is the tonneau cover, which is usually constructed from flexible materials such as leather or vinyl fabric and secured to the bed of the truck, above the floor and usually at the top of the bed walls, by grommets, elastic cords, and the like. These flexible covers are usually secured in place by tie-down ropes extending from eyelets or patches on the four draped sides.
U.S. Pat. No. 3,614,154 discloses a flexible sheet cover material for an open top vehicle wherein the cover edges have edge stiffeners which in combination with tie down cords serve to hold the cover in place. The stiffeners at the cover edges while held under tension in the horizontal position by the tie down cords secured to the stiffeners at fixed points, distribute the stress over a wide area of the cover edges.
U.S. Pat. No. 4,968,085 discloses a truck bed cover for covering loads of varying height. The cover includes a generally rectangular center section of a size adapted to cover the truck bed, surrounded by four outwardly-extending panels or flaps. Each of the flaps is provided with a series of connectors designed to mate with compatible elements located on the truck bed sides. The connectors are arranged on the panels such that the panels may be folded to provide various effective heights for the cover, the folded portions of the panels being maintained in position by complementary fasteners located on the cover.
U.S. Pat. No. 5,431,474 discloses a flexible vehicle cargo cover that has either a single, cord, cable, or strap (or a plurality thereof) which are either housed within a seam that is attached to the perimeter of the cover or are otherwise attached to the perimeter of the cover or are otherwise attached to the cover at the perimeter which includes a plurality of flexible arches that are attached in a concave manner to at least two sides of the cover.
While flexible covers disclosed in the above patents cover the pickup truck bed, they all have certain shortcomings such a tearing under stress. One commonly encountered stress is the stress produced from the downward force which tends to push the cover down into the pickup truck bed from the weight of rain and snow loads. Another commonly encountered stress is the stress produced from the upward force which lifts the cover off the pickup truck bed due to high winds experienced at high transit speeds. Yet another stress commonly encountered is the stress produced when the cover is stretched over the bed of the pickup truck and fastened to the pickup truck body by the tie down straps.
What is needed is a pickup truck bed cover which can distribute these various stresses over the entire surface of the cover to minimize localized stressing which leads to tears.